October 05, 2022
Years published: 2021
NORD gratefully acknowledges Greg Cichon, MD candidate, Creighton School of Medicine and Heather Gomes, MD, Otolaryngologist, Boys Town National Research Hospital, for the preparation of this report.
Pendred syndrome is an uncommon genetic disease in children. Patients usually have hearing loss in both ears (often at birth) and a goiter, which is an enlarged thyroid gland in the neck. The goiter typically grows in the teenage years but may present earlier or later.
Pendred syndrome is caused by the lack of a protein called pendrin, which is important in the kidney, ear and thyroid to keep salt levels balanced. Without enough pendrin, the ion levels become unbalanced and cause hearing and balance issues, a swollen thyroid and less commonly electrolyte imbalances. There is no specific treatment, but the symptoms can be managed with thyroid hormone supplements and hearing aids.
The most common symptoms of Pendred syndrome include:
Pendred syndrome is caused by changes (mutations) in three genes (SLC26A4, FOXI1, or KCNJ10) in about 50% of patients, and the other half are due to unknown causes. Mutations in SLC26A4 (also known as PDS), which encodes the protein pendrin, are the most common identifiable causes of Pendred syndrome. Pendrin is found in the inner ear (responsible for hearing and balance), the thyroid (a butterfly-shaped organ in the lower neck which is responsible for controlling metabolism) and kidneys (responsible for filtering waste and controlling salt levels). Pendrin pumps chloride and iodide to maintain their ion balance in the inner ear, thyroid and kidney. Mutations in these genes result in a lack of pendrin, so the ion levels become unbalanced and cause hearing and balance issues, a swollen thyroid and less commonly electrolyte imbalances.
Pendred syndrome is an autosomal recessive genetic condition. Recessive genetic disorders occur when an individual inherits a non-working gene from each parent. If an individual receives one working gene and one non-working gene for the disease, the person will be a carrier for the disease, but usually will not show symptoms. The risk for two carrier parents to both pass the non-working gene and, therefore, have an affected child is 25% with each pregnancy. The risk to have a child who is a carrier, like the parents, is 50% with each pregnancy. The chance for a child to receive working genes from both parents is 25%. The risk is the same for males and females.
Pendred syndrome affects approximately 2-3 per 1,000 children. This condition is not known to occur more often in people with different racial/ethnic backgrounds.
Hearing loss at birth or during childhood is usually the first sign of this disease. An MRI scan of the inner ear may show an enlarged vestibular aqueduct or an abnormal cochlea. Genetic testing for the pendrin gene is the most common test leading to a diagnosis of Pendred syndrome.
Clinical Testing and Work-up
Abnormal hearing tests lead to the initial suspicion of congenital hearing loss. If possible, an MRI scan of the inner ear may be performed to look for malformations. An MRI does not emit radiation but requires the child to sit still for an extended period. A perchlorate discharge test and thyroid function test may be used to determine how well the thyroid is functioning. The results of these tests will help determine whether the patient needs thyroid hormone supplements or other treatments.
There is no specific treatment for Pendred syndrome and supportive therapies are typically aimed at correcting hearing loss and thyroid dysfunction.
Depending on the extent of hearing loss and thyroid dysfunction, patients with Pendred syndrome may need hearing aids, therapy or thyroid supplements. Patients should be very careful to avoid head injuries, since the inner ear is extra sensitive, and some patients have noted worsened hearing impairment or vertigo after minor head trauma.
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